While the immediate threat has eased, officials said several tankers still must be removed from a bridge that collapsed into the waters of Mantua Creek between here and West Deptford, N.J. And that operation could risk another release of vinyl chloride, a chemical used in the production of plastics that often is transported as a liquid.

"There are cars that are in precarious position," Larry Hajna, a New Jersey Department of Environmental Protection spokesman said at a briefing. "When they have to start moving these cars, you want to make sure they're protected."

At least four tankers in an 84-car freight train had derailed in the accident, he said. But only one had lost its contents.

The vinyl chloride leak from that car appears to have stopped, Hajna said.

"It doesn't appear to be any immense threat" now, he said.

The National Traffic Safety Board has sent a team to investigate the derailment and bridge collapse, according to a statement from the agency.

Officials gave no timetable for the bridge to be cleared, saying the freight rail line's operator, CSX, is obtaining contractors for the job and has called an environmental-response firm to contain the spill in the creek, which flows into the Delaware River about 17 miles south of Philadelphia. The tracks do not carry passenger rail.

"It's got to go a couple days," said Assemblyman John Burzichelli, a Democratic state legislator from Gloucester, N.J.

Burzichelli, also a former Paulsboro mayor, said the community of about 6,000 was resuming its normal routine.

Air pollution from the leak is minimal now, said Larry Ragonese, press director for the state Department of Environmental Protection. The vinyl chloride gas already in the air has dissipated.

Gloucester County officials said 42 people reported to the hospital with respiratory issues, mostly sore throats. Students at schools and residents in three towns were told to shelter in place.

Dr. Bruce Ruck, manager at New Jersey Poison Control, said his agency began getting calls at around 8 a.m. Friday from people who had breathed the fumes, asking about shortness of breath, dizziness and asthma-like symptoms. Officials don't expect residents to have long-term health problems from exposure.

State investigators are trying to assess what else may have leaked into the water from two cars hanging off the train bridge. One may contain plastic pellets, so officials are hoping that only one car might have leaked a chemical into the creek.

The tracks carrying the wrecked train run just feet from the Benny's on the Rail liquor store where Joseph Cinkowski was working.

Cinkowski said he was opening the store around 7 a.m. when he saw the train approach.

"I didn't know if anything happened until about a half hour later," he said. "This person walked in and told me there was a train derailment up the street."

Shortly after that, Cinkowski said he began to smell smoke, "like someone was putting out a fire" followed by police and other safety officials swarming the area and closing off the streets around the crash.

"Residents are free to move about. Traffic is normal," Hajna said. But removing rail cars from the derailment site is "going to be a very delicate move."

It's not clear what caused the derailment, but the same railroad bridge over Mantua Creek collapsed in August 2009, derailing a train carrying coal, according to the Paulsboro Fire Department's website.